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io8

SKULL   OF   ECHIDNA

affairs. It must be remembered, however, that the Cetacea
show the same characters, though it is possible that they too
are developed from .a low mammalian stock. In the vertebral
column we find the typical mammalian seven cervicals; but
those characteristically mammalian structures the epiphyses are

Fia. 51..—Ventral view of skull of Echidna, acid eat ft, and right half of mandible, cmgr,
Angle of mandible ; aud.ass, auditory ossicles ; contt, condyle of inaudible ; cor,
coronoicl process ; wax, maxilla ; oc.cond, occipital eondyle ; pal* palatine ; p.tnasc^
premaxilla; pt, pterygokl j sgr, sqwamosal ; t'j/t tympanic ring. (After Parker and
Haswell.)
totally absent in Echidna,, and only to be seen in the tail-region
in Ornithorliynchus* In having only the capitular head to the
ribs, these mammals are evidently far removed from all other
mammals^ arid are even more reptilian than the Tlieroinorphous
reptiles. The large clavicles and the intercluviclc (Fig. 52,